All-trans-retinoic-acid, known as tretinoin or Retin-A, is an extremely photosensitizing agent used for the treatment of normalizing skin since the 1970's. It works intracellularly, and it organizes the skin, exfoliates it and substantially changes the physiology.
Glycolic acid, an alpha-hydroxy acid, is used in many cosmetic products for improved skin appearance. There are two main theories on how glycolic acid works. The first theory proposes that the glycolic acid produces a mild subclinical irritation which stimulates the epidermis to produce fresh skin, while the second theory proposes that glycolic acid weakens the intercellular bonding of the corneocytes in a manner similar to both water and retinoids. Unfortunately, little objective data regarding the effectiveness of alpha-hydroxy acid has been published thereby leaving the industry to rely on anecdotal information which is difficult to quantify. It is quite clear that many of the topical cosmetics incorporating glycolic acid or other alpha-hydroxy acids have insufficient concentrations to accomplish their objectives.
As stated earlier, some alpha-hydroxy acids have been used in skin treatment. U.S. Pat. No. 4,107,330 discloses a preparation for the treatment of acne containing 0.1 to 10% by weight of thioglycolic acid and the salts, esters, and acid amides thereof, in the treatment of acne. The referenced acne treatment is premised on a sulfur based alpha-hydroxy acid and is not combined with tretinoin.
Since the exact workings of glycolic acid in affecting the skin is unclear, doctors have been reluctant to apply glycolic acid and tretinoin at similar times on patients. Albert Kligman's article "Compatibility of A Glycolic Acid Cream with Topical Tretinoin for the Treatment of the Photo Damaged Face of Older Women" made a tentative conclusion that a topical 8% glycolic acid cream could be used in conjunction with tretinoin to treat photoaged facial skin. Kligman's uncontrolled study required that the subjects apply glycolic acid in the morning and, after washing with Dove.RTM. soap, apply tretinoin at night. Kligman's experiment required separate applications of the two compounds during the day and the two compounds did not simultaneously overlap any skin sites.
Jonathan Weiss and Joel Shavin conducted a similar experiment that is outlined in their article "An Evaluation of the Compatibility of Tretinoin Cream 0.05% and a Glycolic Acid 8% Solution For Acne Prone Skin." They conducted a comparative experiment between tretinoin applied alone, glycolic acid applied alone, and a combination of tretinoin and glycolic acid, each applied separately at different times during the day. The experiment indicated that the effectiveness of tretinoin was not enhanced with the concomitant use of the glycolic acid solution although the tretinoin alone or in combination was superior to the glycolic acid alone.
Accordingly, both glycolic acid and tretinoin, while, in one instance, having been found to have utility in treating photoaged skin through separate treatments during the day, have not been used as a treatment for acne through a cream combining both compounds.
It is thus an object of the present invention to produce a treatment for and inhibition of acne which needs only to be applied once a day combining glycolic acid and tretinoin.